Altered Colonizing Ability for Mouse Large Intestine of a Surface Mutant of a Human Faecal Isolate of Escherichia coli

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Abstract
E. coli F-17 Sr, a human fecal isolate, is resistant to the T-series of bacteriophages (i.e., T2 to T7). A T2-sensitive mutant of E. coli F-17 Sr was isolated following acriflavin treatment. This mutant, E. coli F-17 Sr Ts, was sensitive to the entire T-series of phages. E. coli F-17 Sr and E. coli F-17 Sr Ts did not differ quantitatively in total LPS [lipopolysaccharide] content. Analysis of LPS revealed that a large fraction of E. coli F-17 Sr Ts was devoid of O side-chains. This accounted for the sensitivity of this strain to bacteriophages T3, T4 and T7. E. coli F-17 Sr Ts contained only about half the amount of capsular material contained by E. coli F-17 Sr, accounting for the sensitivity of the mutant to bacteriophages T2, T5 and T6. Although the 2 strains colonized equally well when fed individually to streptomycin-treated mice, when fed simultaneously to streptomycin-treated mice, E. coli F-17 Sr Ts colonized at a level of .apprx. 1 .times. 108 cell/g feces and E. coli F-17 Sr colonized at only 1 .times. 104 cells g/feces. Apparently, bacterial cell surface components modulate the large intestine colonizing ability of E. coli F-17 Sr in the mouse large intestine.

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